Update on UFOs

Machine Protection PanelMay, 13th 2011 1

Update on UFOs

Tobias BärMPPMay, 13th 2011

Acknowledgements: E. B. Holzer, S. Jackson, M. Misiowiec, E. Nebot, A. Nordt, J. Wenninger, C. Zamantzas

2Machine Protection PanelMay, 13th 2011

Content

1. UFO Detection and Data Processing

2. Observations

3. Outlook and Summary


Content


2. Observations



UFOs in 2011

• UFO Buster detects UFOs online in 1Hz concentrator data.Losses (RS 4) of two BLMs in 40m are above 1E-4 Gy/s.RS 2 / RS 1 > 0.55 (UFO average : 0.89).RS 3 / RS 2 > 0.45 (UFO average: 0.79).

• Over 4000 triggers by the UFO Buster so far.

• From subset of 230 manually verified triggers: About 70% are UFOs, 10% ambiguous cases, 20% are false triggers.

• For most analysis additional cut. E.g.:Only flat top UFOs, loss of UFO BLM (RS05) > 5 10∙ -4 Gy/s (≈ 5 ‰ of

threshold).53 events remain of subset, of which 51 are clear UFOs (96%) and 2 are

ambiguous cases.


Content


2. Observations



UFOs Below Threshold

Most UFOs are much below threshold.

628 candidate UFOs at 3.5 TeV.Signal RS05 > 5∙10-4 Gy/s.

NICE

exponential fit


Spatial UFO Distribution

3.5 TeV628 candidate UFOs.

Signal RS05 > 5∙10-4 Gy/s.

The UFOs are distributed all around the machine.

38 candidate UFOs at MKI for Beam 2.

450 GeV137 candidate UFOs.

Signal RS05 > 5∙10-4 Gy/s.

Mainly UFOs at MKIs

NICE

significant increase at MKI.R8


UFO rate

On average: 10 UFOs/hour 1978 candidate UFOs at 3.5 TeV. Data scaled with 0.7669 (detection efficiency from reference data)

336

b 7

2 bp

i48

0 b

36

bpi

336

b 7

2 bp

i48

0 b

36

bpi

624

b 7

2 bp

i

768

b 7

2 bp

i

480

b 7

2 bp

i


UFOs at MKIs

• Since 08.04.2011 in total 460 fast loss events around MKIs. (104 around MKI in IP2, 336 around MKI in IP8).

Distribution of first BLM which sees the loss:

Left of IP2 Right of IP8


Example: UFOs at MKI R8

UFO at 1424 GeV, 768 bunches. Loss starts at BLMQI.04R8.B1I30_MQY.

UFO at 2352 GeV, 228 bunches. Loss starts at BLMEI.05R8.B2E10_MKI.C5R8.B2.


Energy Distribution of MKI UFOs

Many events at 450 GeV.

244 candidate UFOs at MKIs after scrubbing run. No cuts.


MKI UFOs During Scrubbing

• Typical scenario for MKI UFOs during scrubbing: Loss spikes occur in first few minutes after an injection and go away then.

2 hours


Dump on 01.05.2011

Dump of BLMQI.04L2.B1E20_MQY on RS 3, 4 and 5


Dump on 01.05.2011

• From fit of PM data (BLMEI.05L2.B1E10_MKI.D5L2.B1):

Amplitude: 0.63 Gy/sWidth: 0.29 ms


Dump by ALICE on 14.04.2011

Could be a UFino


Dump by ALICE on 14.04.2011

• From fit of PM data (BLMEI.01L2.B1I10_MBWMD):

Amplitude: 6.3 10∙ -4 Gy/sWidth: 0.16 ms


Content


2. Observations



Next Steps

• Trigger acquisition of turn-by-turn data.UFO Buster kernel integrated in BLM

Concentrator.Successful test during technical stop.

• Better localization of MKI UFOsSimulations (Yngve – BDSIM)Additional BLMs


Summary

• About 3000 candidate UFOs in 2011 so far.2 UFOs were dumping the beam.Most events at 3.5 TeV.

• UFO rate in last weeks constant.10 UFOs/hour at 3.5 TeV.

• Many UFOs at MKIs.

• Next step: improve the diagnosticsUFO Buffer with 80μs BLM data.Additional BLMs at MKIs.


Thank you for your Attention

Tobias BaerCERN BE/[email protected]: +41 22 76 75379

Further information:• E.B. Holzer, “Losses away from collimators: statistics and extrapolation”,

LHC Beam Operation Workshop, Evian, December 2010.

• T. Baer, “LHC Machine Protection and UFOs”, DPG Spring Meeting, Karlsruhe, March 2011.

• J. Wenninger, “Analysis attempt of dump UFOs”, LHC Machine Protection Panel, Geneva, March 2011.


Backup slides


UFO Detection

• UFO Buster detects UFOs online in 1Hz concentrator data.

1. Losses (RS 4) of at least two BLMs within 40m are above 1E-4 Gy/s.

2. A BLM is not taken into account ifIt is a BLMES, BLMCC, BLMDS, BLMDI.It is at a TCT or TDI.It is in IP3, IP6, IP7 or IP8 (between TCTs).RS 2 / RS 1 < 0.55 (UFO average: 0.89).RS 3 / RS 2 < 0.45 (UFO average: 0.79).

3. The acquisition is skipped for a few seconds after injection warning and beam wire scan timing event.


UFOs in 2010

• 18 beam dumps due to UFOs.(since 07.07.2010)

• 113 UFOs below threshold foundin logging database. (E. Nebot)

(03.08.2010 - 28.10.2010)

• UFO rate proportional to intensity.

• No dependency of peak signal on intensity. (cf. E.B. Holzer at Evian Dec. 2010)

• Loss duration has tendency to become faster with higher intensity. (cf. E.B. Holzer at Evian Dec. 2010)

J. W

enni

nger


Fast Loss Event Rate

• After the increase of the BLM Threshold by a factor of 3 there were about 4.1 times less beam dumps due to fast loss events.


Peak Signal and Loss Duration

• Average UFO signal: no clear dependence on intensity

• Loss duration: tendency to decrease with intensity

courtesy ofE. B. Holzer and E. Nebot


UFO size

• Two extreme cases:• UFO much larger than beam: the beam is imaging the UFO.

• UFO much smaller than beam: the UFO is imaging the beam.

Most UFO shapes are Gaussian, thus most UFOs are expected to be smaller than the beam.

• From FLUKA simulations: size ≈ 1 μm.(cf. M. Sapinski, F. Zimmermann at Chamonix 2011)

courtesy ofJ. Wenninger

(cf. MPP 25.03.2011)


UFO Speed

• UFO speed:

• From free fall:

The UFO speed corresponds to the expected speed for a free fall from the aperture.

T

b

T

UbUv

22

vu: UFO speed, σb: transverse beam size, σu: UFO size,

σT: temporal width of loss.

22 m

m f

ree

fall

εnorm = 2.5 µm·radβ = 150 m

sm

U hgv 63.02


Example: Loss at MKI for B1

• Loss starts at BLMEI.05L2.B1E20_MKI.C5L2.B1

• BLMQI.04L2.B1E20_MQY at 98% of dump threshold (RS5)

• At 3.5 TeV stable beams.


Lossratio for MKI UFOs B1

104 candidate UFOs around MKI for B1, no cuts.


Lossratio for MKI UFOs B2

336 candidate UFOs around MKI for B2, no cuts.


Dynamics of Dust Particles

From simulations:

• Dust particle will be positively ionized and be repelled from the beam.

Beam intensity: 2.3 10∙ 12 protons, Al object.

• Loss duration of a few ms.Losses become shorter for larger beam intensities.

courtesy ofF. Zimmermann


Known Dust Particle Sources

• Distributed ion pumps (PF-AR, HERA).

• Electrical Discharges (PF-AR).

• Movable Devices.

• Particles frozen or condensated at cold elements. (ANKA)

Update on UFOs

Documents

thresholdmost ufos

clear ufos

tev628 candidate ufos

gev137 candidate ufos

mki r8 ufo

ufo average

bpi480 b

loss of ufo blm rs05